1. Field of the Invention
The present invention relates to a plan executing apparatus which executes an interrupting plan, a method of plan execution, and a computer program product therefor.
2. Description of the Related Art
During an execution of a plan, which is a predetermined task sequence, an execution of another plan is sometimes required as an interrupt. A known technique for execution management of such an interrupting plan is called scheduling. According to one known technique of scheduling, when there are plural interrupts, the interrupts are ordered according to their priorities (see, for example Japanese Patent Application Laid-Open No. 06-187171).
When such a technique is employed for a mobile robot, however, the mobile robot may move to a different location. If an execution of an interrupting plan is allowed during execution of another plan, then the mobile robot may move to a location where the execution of the interrupted plan is impossible.
For example, assume that an execution of a task “climb the stairs” is interrupted by a task “go to the living room.” After the execution of the interrupting task, the mobile robot is in the living room where the mobile robot cannot resume and accomplish the interrupted task even if the robot is instructed to restore the interrupted task, “climb the stairs.”
Thus, when an execution of a certain task is influenced by an object on which the task is executed, and at the same time, the execution of the task brings about a change in state of the object, task management cannot be carried out in the conventional manner.